Controllers to start and stop irrigation cycles without human intervention are well known. These controllers send an electric current (usually 24 volt alternating current in horticultural or agricultural use) to a remote solenoid valve, causing the valve to open. Valve closure is usually effected by discontinuing the supply of electric current to the solenoid of the valve whereupon the valve is caused to close.
Most of these types of controllers are able to handle a number of valves, opening and closing them in a programmed succession for programmed times on programmed days of the week. This series of sequential valve opening and closing on specified days is generally referred to as "a program" or "an irrigation program". Many of the known controllers are capable of storing and executing more than one irrigation program, which adds a degree of flexibility to what the controller may accomplish.
Basically these prior controllers fall into one of three categories as follows:
1. Relatively inexpensive controllers which are capable of executing an irrigation program. These controllers are not capable of changing the set irrigation program in any way to take account of differing water needs of plants occasioned by variations in meteorological conditions. PA1 2. More expensive controllers which can alter the frequency and amount of irrigation, either up or down, as time passes in an effort to match applications to plant requirements. Such devices usually impute likely plant requirements by use of meteorological averages developed from examination of many years of meteorological records relating to the geographical area under consideration. This type of controller is an improvement upon the first described type of controller, but is still arbitrary and inflexible as it relies on averages which must inevitably waste water when the predicted conditions do not occur. Additionally, there can be no improvement in harvesting rainfall. PA1 3. Expensive controllers which either accept direct input from an automatic weather stations, or accept meteorological information directly or indirectly from a remote weather station or climatic recording facility. These controllers use such information to modify a basic program so that irrigation water applications are substantially in accord with actual plant requirements. These controllers may also be activated to apply a predetermined irrigation cycle when instructed to do so by a remote software program which accepts meteorological input and maintains a water budget for the area. However, such controllers do not utilise localised rainfall measurement and consequently irrigation management depends upon rainfall information indicative of a wider area than the irrigation area. Water wastage can result. Further, these controllers must be part of a very wide network which means that over a wide area very considerable telephony or radio costs are necessarily involved. PA1 (a) at least one first means to measure one or more weather conditions in a first area; PA1 (b) at least one second means to measure rainfall in a sub-area of the first area; and PA1 (c) control means connected directly or indirectly to the first and second means, the control means adapted to monitor the measurements of the first and second means, to calculate a moisture content value for the sub-area from the measurements and a predetermined moisture loss for the sub-area, and to regulate the irrigation in a sub-area. PA1 (a) measuring one or more weather conditions in a first area; PA1 (b) measuring rainfall in a sub-area of the first area; PA1 (c) monitoring the measurements; PA1 (d) calculating a moisture content value for the sub-area from the measurements and a predetermined moisture loss for the sub-area; and PA1 (e) regulating the irrigation of the sub-area.
Controllers of this type constitute well over 90 per cent of all irrigation controllers currently in use in Australia. Such controllers will, if the irrigation program is not regularly modified inevitably waste considerable quantities of water, since it will be programmed to supply sufficient water to serve the needs of the plant being irrigated during periods when plant demand for water is high. PA2 Thus when the same application of irrigation water continue during periods of low plant water requirement, wastage occurs. PA2 Additionally, such controllers are incapable of responding to occurrence of rain periods unless coupled to some specialist sensor designed for the purpose. Whilst such sensors are known they tend to be either expensive (and consequently little used) or unreliable (and again little used). The potential to save water by in effect harvesting rainfall by discontinuing irrigations until that rainfall finds its way into the root-zone and is transpired by the plants, is lost unless the controller can be manually de-activated. When managing large numbers of such controllers, particularly over a wide area, it is generally not possible to manually de-activate them and re-activate them when irrigation should commence.